The invention relates generally to monitoring systems. More particularly, the invention relates to systems and methods for real-time monitoring and measuring of transient phenomena.
Transient phenomena pose a serious threat to systems exposed to such phenomena. Transients can occur at any time with varying amplitude, frequency, and duration. The magnitude or energy content of the transient phenomena can affect the electronic and mechanical components of these systems to cause permanent or temporary malfunction. Because of the destructive potential of transients, industry has developed various transient monitoring systems for detecting and measuring transients that occur near important or critical systems.
Lightning is one potentially destructive transient phenomenon. For example, current spacecraft launching procedures typically suspend launch operations should lightning occur directly or nearby until system level tests are performed to ensure that electromagnetic transients produced by the lightning have not damaged or disturbed the payload or launch vehicle systems. These retest operations are costly and often unnecessary. By strategically placing electromagnetic sensors near the payload and launch vehicles, an assessment of the potential damage caused by lightning-induced transients can be made by evaluating the transient information captured by the sensors.
Transient monitoring systems measure certain key parameters that are indicative of the potentially destructive nature of detected transients. For lightning-induced electromagnetic transients, for example, key parameters include positive and negative peak amplitudes, and duration, energies, and maximum rates-of-change or rise-times of positive and negative transients. Often, such parameters are empirically determined to correlate to problems experienced by electronic systems due to transients.
To characterize key parameters of transient phenomena, conventional transient monitoring systems digitize the analog input signal and save the digital data in memory for subsequent download and evaluation. A disadvantage of this technique is that the digital data must be post-processed, thus the characterization of the key parameters is not available in real time. Secondly, while the digital data is being downloaded from the memory, the system is offline, that is, the system is not collecting additional digital data. For applications monitoring transient events, input transients will go undetected if they occur during this transfer period. Repetitive or closely-grouped high frequency transients, such as those that occur with lightning, increase the likelihood of a missed transient. The loss of such information can lead to an erroneous and potentially catastrophic conclusion that the monitored system has not been exposed to harmful transients.
Objectives of the present invention are to provide a transient pulse monitor that is capable of measuring transients in real-time and to perform such real-time measurements without experiencing dead time, i.e., a period during which the monitor can miss a transient. Another objective is to make accurate real-time measurements. Yet another objective is for the monitor to process large amounts of data with minimal data storage. Still another objective is for the monitor to be readily reconfigurable.
In brief overview, the system and method of the invention feature continuously receiving an input analog signal; continuously sampling and digitizing the analog signal; buffering the digitized data; computing in real-time from the digitized data a parameter value that represents a characteristic of the stimulus; discarding the digitized data after the data is used to compute the parameter value; outputting computed parameter values, for example, to a system bus or to a storage medium; and continuing to sample, digitize, and buffer while outputting the parameter values to the system bus or storage medium, so as not to miss any transients that may have occurred during this period.
In one aspect, the invention features a system for characterizing a stimulus represented by an analog signal. Conversion circuitry continuously receives the analog signal and converts the analog signal into digital data. Digital circuitry continuously receives the digital data from the conversion circuitry. The digital circuitry dynamically computes from the digital data a value that characterizes a parameter of the stimulus while the digital circuitry continuously receives new digital data from the conversion circuitry. In one embodiment, the digital circuitry is re-programmable so as to be capable of characterizing a different parameter or parameters of the same or of a different type of stimulus. The conversion circuitry and the digital circuitry can be provided on the same or different integrated circuit chips, on the same or different circuit boards, and in a computer system or other electronic device, such as a meter.
In accordance with the type of transients being monitored, the system characterizes certain key parameters. For example, for electromagnetic transients, the characterized parameters include positive and negative peak amplitudes, duration of positive and negative transients, the rate of rise of the positive and negative transients, and energy.
The system includes a program memory storing a first program. In one embodiment, a digital signal processor is in communication with the program memory and computes the value that characterizes the parameter according to the first program. In another embodiment, the system includes programmable logic in communication with the digital signal processor. In this embodiment, the programmable logic computes the value that characterizes a second parameter as directed by the first program. Also, the programmable logic is reprogrammable by the digital signal processor as directed by the second program. In still another embodiment, the digital transient pulse monitoring system includes self-test circuitry.
The digital circuitry is in communication with a bus. While the digital circuitry outputs the computed value over the bus, the digital circuitry continuously receives new digital data from the conversion circuitry. The conversion circuitry can include a signal conditioner that receives the analog signal and modifies the analog signal to produce a modified analog signal having a particular voltage range.
In another aspect, the invention features a system that includes an analog-to-digital converter, a processing unit, and a memory buffer. The analog-to-digital converter receives an analog signal representing a stimulus and converts the analog signal into digital data. The processing unit dynamically computes from the digital data a value that characterizes a parameter of the stimulus. The memory buffer is in communication between the analog-to-digital converter and the processing unit and continuously receives new digital data from the analog-to-digital converter while the processing unit processes digital data obtained from the memory buffer to compute the parameter value. The rate at which the memory buffer receives new digital data from the A/D converter is less than the rate at which the processing unit receives digital data from the memory buffer. In one embodiment, the processing unit continuously obtains digital data from the memory buffer except while the processing unit is outputting a computed value.
In one embodiment, the processing unit includes a digital signal processor. The system can also include programmable logic in communication with the memory buffer to receive concurrently the same digital data that are received by the digital signal processor. The programmable logic and the digital signal processor dynamically compute, from the same digital data, values that characterize different parameters of the stimulus. Thus, in this embodiment, digital data passes from the memory buffer to the programmable logic and the digital signal processor concurrently, and while the digital signal processor characterizes a first parameter (e.g., energy), the programmable logic computes a second parameter (e.g., peak amplitude).
In another aspect, the invention features a method of characterizing a stimulus represented by an analog signal. Digital data are continuously received. These digital data are digitized from the analog signal representing the stimulus. A value that characterizes a parameter of the stimulus is dynamically computed from the continuously received digital data while new digital data, digitized from the analog signal representing the stimulus, are received. The new digital data that are received while the computed value is being outputted, for example, to a storage medium, are stored for subsequent processing. The continuously received digital data are processed at a rate that is greater than a rate at which the new digital data are received.